Celestron FIRSTSCOPE 80 EQ Instruction Manual page 12

There are numerous optional eyepieces that are available to expand your range of magnification.
There are various types of eyepieces of varying quality to choose from.
B. Eyepieces come in barrel diameters of .96" and 1-1/4". In general, the 1-1/4" eyepieces are of a higher
optical quality and give you sharper images along with a wider field of view and better eye relief.
C. Magnification through the telescope has its limits. These limits are determined by the laws of optics
and the nature of the human eye. The maximum usable power is equal to 60 times the aperture of the
telescope (in inches). So your telescope has a maximum useful power of 188x (3.14" x 60). You can
create power higher than this limit but the images will be dark and blurred.
The maximum power is used only under ideal conditions which are not common. Most of your
viewing will be done in the range of 35x to 150x. Higher powers are used mainly for lunar and
planetary observing.
D. Your telescope comes equipped for use with both .96" and 1-1/4" eyepieces.
The eyepiece adapter (#8) is set up for usage of .96" size eyepieces. The inner bushing is easily
removed so that 1-1/4" eyepieces can be used.
F. When changing eyepieces, you will have to refocus by turning the focusing knob (#9).
6. TELESCOPE OPERATION—ASTRONOMICAL OBSERVING
After you have read and followed the instruction manual to this point, the telescope is set up and you
are ready to begin your observing adventure.
To enable you to find objects you should have a set of Star Charts. The location of the planets may
appear in local newspapers.
A, The Moon is an awesome first object to observe. The best observing occurs during the partial phases
as a full Moon is too bright.
At low power you can see the complete Moon and at high powers you can see lunar details such as
mountain ranges, craters and rills.
B. Five of the planets are easy targets for your telescope.
1. See Jupiter with its great red spot, study the cloud bands and watch its moons shuttle back and
forth.
2. Study Saturn and its splendid ring structure.
3. Observe Mars and see its polar cap.
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